अथ हैन प्रतिहर्तोपससाद प्रतिहर्तर्यादेवता प्रतिहारमन्वायत्ता ता चेदविद्वान्प्रतिहरिष्यसि मूर्धा ते विपतिष्यतीतिमा भगवानवोचत्कतमा सा देवतेति ॥
In plain words
Then the pratihartṛ priest approached him and said: 'Venerable sir, did you not tell me: If you perform the pratihāra without knowing its deity, your head will fall off? Which is that deity?'
Close to the Sanskrit
Then the pratihartṛ approached him: 'O pratihartṛ, if you chant the pratihāra without knowing the deity connected to the pratihāra, your head will fall off' — thus did the venerable one speak to me? Which is that deity?